My 13" Unibody MacBook Pro had been experiencing erratic trackpad behavior. After digging around online, I decided to test the theory that it was caused by a bulging/overheating battery rather than the trackpad itself.
The investigate this as scientifically as possible, I had to remove the battery and use the MacBook plugged in. Of course, on the unibody models, the battery is "not user replaceable" and locked in by tri-wing screws - so I bought the 54 bit kit which was supposed to include them.
Unfortunately, I received a kit with duplicate bits and missing the ones I needed. My replacement is still in the mail. Customer service was prompt and friendly in solving this. After I receive it, should I find my battery is in fact the problem, I will be purchasing a new one from ifixit.